Add gridArea to unitless CSS properties

[mgol]

Ref #9185

Based on jquery/jquery@f997241

grid-area accepts a numeric value which then translates to grid-row-start, setting grid-row-end, grid-column-start & grid-column-end to auto.

I thought about adding a test but I don't understand how the ones in CSSPropertyOperations-test.js are supposed to work. For example, setting grid-row to 10 will result in a normalized gridRow style property with a value "10 / auto". It seems they work just because they use ms-prefixed properties in format not actually used in IE as IE's grid properties were named differently?

Another remark - in jQuery we have been auto-appending px to most numerical values as well but we decided it was a bad decision. It doesn't scale as it requires us to add more & more properties to the list. We've actually exposed the list at jQuery.cssNumber so that people don't always have to wait for us to add support for a property and do a release. What's more confusing, some of them would work both with & without the px suffix and that changes the meaning.

That's why we decided that in jQuery 4 we'll drop the auto-prefixing blacklist and turn to a whitelist that lists only a few most common properties to which we want to auto-append px (mostly because they're extremely common and we don't want to break the world too much); we plan to not expand that list. You can see the current plan in my PR: jquery/jquery#4055. In particular, see the proposed whitelist in a (visualized) regexp in:
https://github.com/jquery/jquery/blob/03e9dba3882868e1ee79f1fb0504326da925644f/src/css/isAutoPx.js.
Something to consider for a future React version.

[pull-bot]

Details of bundled changes.

Comparing: 877f8bc...c4f1d23

schedule

File	Filesize Diff	Gzip Diff	Prev Size	Current Size	Prev Gzip	Current Gzip	ENV
schedule.development.js	n/a	n/a	0 B	19.17 KB	0 B	5.74 KB	UMD_DEV
schedule.production.min.js	n/a	n/a	0 B	3.16 KB	0 B	1.53 KB	UMD_PROD

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[gaearon]

Do you mind filing a separate issue with your proposal?

[mgol]

@gaearon I submitted #13567 with the proposal.